A road vehicle comprises a powertrain system, which is provided with an engine which generates a torque, and with a driveline which transmits the torque generated by the engine to the road surface; e.g. in a front-wheel drive car provided with an internal combustion engine, the driveline comprises a clutch, a gearbox, a differential, two axles shafts and two wheels each presenting a metallic rim supporting a rubber tire.
A powertrain system of a road vehicle presents a characteristic mechanical inertia and a characteristic torsional elasticity, i.e. to transmit the torque generated by the engine all the components of the powertrain system must undergo a torsional deformation or a torsion which may be more or less accentuated according to the mechanical features of each component. When a sudden variation in the torque transmission occurs (e.g. when the clutch is rapidly released with the gear engaged and the drive wheels have a good grip on the road surface), such a variation of the torque determines a corresponding variation in the longitudinal acceleration of the vehicle. Due to the torsional elasticity present in the powertrain system, a step variation of the torque triggers oscillations in the longitudinal vehicle acceleration about a final value which are progressively damped. Such oscillations in the longitudinal acceleration of the vehicle are damped rather rapidly (in the order of a few seconds); however, if not effectively counterbalanced, they are clearly perceived by the vehicle occupants and thus they are annoying.
In order to eliminate the oscillations in the longitudinal acceleration of the vehicle triggered by a variation of the torque generated by the engine, it has been suggested to implement a maximum damping algorithm in the torque control strategy. The use of a maximum damping algorithm is effective, because it is capable of either completely or nearly completely eliminating the oscillations in the longitudinal acceleration of the vehicle, but not very efficient, because it determines a considerable deceleration of the load increase of the transmission system, thus compromising the vehicle dynamic reactivity, in a manner perceivable by the driver.